Quorum systems are well-known techniques designed to
enhance the performance of distributed systems, such as to reduce
the access cost per operation, to balance the load, and to improve
the system scalability. All of these properties make quorum systems
particularly attractive for large-scale sensor applications
involving coordinated tasks, such as rescue applications. In this
paper we analyze quorum techniques in the specific context of sensor
networks and energy conservation, and show why quorum systems
designed for wired networks and their metrics fail to address the
challenges introduced by sensor networks. We then redefine quorum
metrics such as access cost, load balance, and capacity in a way
that takes into account the limitations and the characteristics of
sensor networks, and discuss some energy-efficient design
strategies. In addition, we propose a family of energy-efficient
quorum systems and a particular construction, called Regional
Quorum system (RQ), which reduces the quorum access cost. Finally,
we propose a data diffusion protocol built on top of the RQ system,
which improves energy consumption by reducing message transmissions
and collisions, and increases the available bandwidth. We apply our
diffusion protocol to analyze the RQ system using our novel
metrics.